Cu–amine coordinated PVDF membranes with superhydrophilic/underwater-superoleophobic surfaces for high-flux and durable antifouling in industrial wastewater treatment

The development of membranes that combine high permeability with robust antifouling performance is critical for efficient separation in complex wastewater systems. In this work, a Cu-functionalization strategy for PVDF membranes (Cu-m) is presented based on catechol-assisted APTES functionalization followed by Cu²⁺ coordination, enabling precise regulation of surface chemistry and interfacial behavior. An optimized precursor composition (APTES: 1 mL; Cu²⁺: 0.3 g) yielded membranes exhibiting superhydrophilicity and underwater superoleophobicity, while structural and chemical characterizations confirmed successful silane grafting and homogeneous Cu incorporation via stable Cu–amine coordination. Under pure-water permeation conditions, the optimized Cu-m achieved an ultrahigh flux of 9895.4 L m⁻² h⁻¹ bar⁻¹. During oil–water separation, the membrane exhibited excellent antifouling performance, maintaining a flux recovery of over 90% after 100 filtration cycles. Hermia's fouling model analysis revealed a transition in the dominant fouling mechanism from surface-driven cake layer formation in pristine PVDF to internal pore blocking in Cu-m, indicating that coordination-driven surface modification fundamentally alters oil–membrane interactions and fouling pathways. In addition, the Cu-m demonstrated strong chemical stability under both acidic and alkaline conditions owing to robust Cu–amine and Si–O–C bonding. Overall, this study demonstrates that coordination chemistry can function as a mechanistic lever to simultaneously optimize permeability, fouling resistance, and chemical durability, highlighting the potential of Cu-functionalized PVDF membranes for high-performance oil–water separation and industrial wastewater treatment.